From 2—10 August 2024 the Seventh Paleontological Expedition of the National Museum of Natural History, Sofia (NMNHS) took place at the fossil locality containing remains of dinosaurs and other vertebrate fauna of Late Cretaceous age near the town of Tran. The team led by Assoc. Prof. Latinka Hristova included Assist. Vladimir Nikolov and specialist Ralitsa Bogdanova from NMNHS, Prof. Marlena Yaneva and Assoc. Prof. Lubomir Metodiev from the Institute of Geology at the Bulgarian Academy of Sciences, as well as volunteers Gergana Velyanova from the Institute of Mineralogy and Crystallography at the Bulgarian Academy of Sciences and Georgi Sevov.
As a result of the team's activities, about 30 new vertebrate fossils were collected, which not only enrich the palaeontological scientific collection of NMNHS, but will also allow palaeontologists to reveal more details about what the animal world looked like in the area more than 80 million years ago.
The discovered fossils are diverse, but for yet another year the fragments of turtle shells are the most numerous. Among the more interesting specimens is an almost completely preserved bone of a large reptile, probably a dinosaur, discovered by the palaeontologist Ralitsa Bogdanova from NMNHS. The bone is relatively well preserved, but badly cracked, which required it to be removed from the rock using a protective plaster jacket. It was transported safely to Sofia, where it will be cleaned and the species of the animal will be determined.
An interesting fact is that in the rock layer in which the bone was found, previously only the remains of amphibians and fish have been found through an examination of sediment samples in laboratory conditions.
Among the other fossils found by the palaeontologists are three crocodylomorph teeth, two teeth of other animals and a bony fish scale, as well as fragments of amphibian limb bones. In addition to the vertebrate remains, palaeontologists found numerous fossilised plant seeds and nuts, suggesting that the vegetation in the area was quite diverse.
Of significant interest are two miniature fossils of currently unspecified taxonomic affiliation, which resemble fossils found in the Upper Cretaceous sedimentary rocks of Central Europe, believed to be insect eggs. If this is confirmed, the findings from the fossil locality near Tran will be the first evidence of Mesozoic insects in Bulgaria.
In addition to their work at the fossil site, the researchers made field prospections around Tran and nearby villages, looking for new rock outcrops of sedimentary deposits which might be containing vertebrate fossils. At one of the sites visited, the team identified a succession of sedimentary rocks the characteristics of which appear to be similar to those of the dinosaur-bearing deposits near Tran. Similar types of plant remains were also observed there. Based on the rock samples collected by the scientists, analyses will be carried out to determine the age of the sedimentary deposits and the characteristics of the natural environment in which they were accumulated. The results of these analyses are expected to show if this new location bears the potential to become a new Upper Cretaceous fossil vertebrate site in Bulgaria.
The seventh expedition to the palaeontological site near the town of Tran was financially supported by the Bulgarian National Science Fund under project No. KP-06-N44/6.